What is the meaning of humdrum?

noun

• The quality of wearisome constancy, routine, and lack of variety.
  • usage: "he had never grown accustomed to the monotony of his work"; "he was sick of the humdrum of his fellow prisoners"; "he hated the sameness of the food the college served"
  • synonyms: monotony, sameness

adjective

• Not challenging; dull and lacking excitement.
  • usage: "an unglamorous job greasing engines"
  • synonyms: commonplace, prosaic, unglamorous, unglamourous
• Tediously repetitious or lacking in variety.
  • usage: "a humdrum existence; all work and no play"; "nothing is so monotonous as the sea"
  • synonyms: monotonous